SIMULATION: Transactions of The Society for Modeling and Simulation International

Veerapandian, M.; Ramani, S.

doi: 10.1177/003754977502400605pmid: N/A

This paper discusses the use of a GPSS/360 simulation model to analyze the bus service of the metropolitan bus system in Madras, India. The system has been unable to obtain enough buses to keep pace with demand and has waged a constant battle to keep its existing buses rolling. The factors contributing to the system's major operational problems have been identified and incorporated in the model. A comparison of the model's output with historical data shows that it is suitable for analyzing operational pro blems, and it is expected to be useful for tactical planning and for improving future operations.

Webb, Warren L.; Schroeder, Henry J.; Norris, Logan A.

doi: 10.1177/003754977502400602pmid: N/A

This paper presents a computer model of the movement of pesticide residues in a forest ecosystem. As such, the paper deals primarily with the potential direct effects on target and nontarget organisms, but does not address the very long-term consequences of restructuring the vegetation in an ecosystem. Simulations using the model trace the movement of two herbicides (2,4,5-T and picloram) through two different environments, one typical of an Oregon forest and the other typical of southern California chaparral. The model is written in DYNAMO.

doi: 10.1177/003754977502400603pmid: N/A

Naylor, Thomas H.; Jeffress, Charles

doi: 10.1177/003754977502400604pmid: N/A

Within a period of less than five years, computer- simulation techniques have penetrated corporations in the United States, Canada, and Europe at the highest possible level. This paper summarizes the results of a survey of 346 corporations, most of which are either using, developing, or planning to develop some form of corporate simulation model. Among the questions addressed by the survey for which empirical answers have been sought are: Who is actually using corporate simulation models? Why are they being used? What resources are required to develop them? What techniques are employed? How much do they cost? What are the benefits to be derived from their use?The paper concludes with a series of specific recom mendations for improving the effectiveness of cor porate simulation models. First, corporate models should be made more user-oriented. Second, more attention needs to be given to the production acti vities of firms. Third, the possibility of inte grating optimization models into corporate models needs to be explored further. Fourth, financial, marketing, and production models should be linked together. Fifth, the use of models to simulate the global environment of corporations should be con sidered. Sixth, greater emphasis should be placed on the "politics" of corporate model building.

Blanning, Robert W.

doi: 10.1177/003754977502400606pmid: N/A

This paper suggests a computationally economical alternative to the common method of using simulation for sensitivity studies, i.e., by making repeated simulation runs with incrementally changed inputs and then observing the magnitudes of the resulting changes in the outputs of interest. Although no theory now exists for constructing the requisite "metamodels" for direct sensitivity analysis, it is possible to construct them, as is illustrated by three examples in the field of operations research.

Hecht, Volker; Reuss, Walter; Rzehak, Helmut

doi: 10.1177/003754977502400607pmid: N/A

This paper describes a hybrid compiler system which enables a user to program the analog and digital portions in a homogeneous language. The features of a well-suited language are deduced. The boundary of the analog and digital regions is optional. It is shown that this degree of freedom is necessary to permit transfer of programs from one machine to another. The compiler requires use of an autopatch system which is described. An algorithm is presented for mapping the analog part of the problem into the switching network of the autopatch system.